Can any existing electric be refinished? Reasons I'm imagining not might be something to do with existing finish, I guess. Can sunburst finishes be redone, for example?

Can a refinish adversely effect the sound of a guitar?

Can any guitar have body binding added? Obviously nothing that's heavily contoured can but what about something like a Les Paul Jr that is essentially uncountoured but has it's edges softened as when stock, it's unbound?

Am I right in thinking a truly authentic nitro-cellulose finish is now unusual/unavailable given environmental concerns? In Europe at least.

Any finish can be redone, and yes, it can be nitrocellulose of you want. I spray nitro on guitars , both from cans and from a spray guns (though without a proper workshop, I have to rely on the weather as I really have to work outside so it has to be warmish and not too windy). Nitro is nasty stuff, so you need a decent vapour mask, gloves and goggles when using it, and it must be in a well ventilated environment.

The big caveat is that you are normally talking about stripping the finish completely from the original guitar. Easy enough with nitro, acrylic and polyurethane, but a guitar with a polyester finish is a real pain to strip. And stripping takes quite a lot of time, so it costs a lot to have done professionally.

The danger with stripping is that with cheaper guitars with a veneer top rather than a solid piece of timber, is that you will probably sand through the veneer in order to get back to the wood. Not a problem if you want a solid colour, but you have to be very careful indeed if you want to refinish a thin veneered flame maple (standard finishing veneer is 0.5mm-0.6mm thick).

Yes, a very thick finish can dull the resonance of a guitar, but by the time you've sanded down the existing finish to take new paint (if not completely removing but over-spraying like a lot of old Fenders were), sprayed on your new colour and clear coats then sanded that back flat and then polished up to a shine, then you aren't really adding much thickness if done carefully.

If spraying a different type of finish on top of an existing finish, then you have to be sure that the finishes are compatible and don't chemically react. It's always best to stick with the same finish type if possible, when not stripping.

Yes, it is possible to add binding to a non-bound body, as long as the rounded edge doesn't have too great a radius. You may have to use a thicker binding than would normally be used on edges where they are a bit too round. A 1.5mm radius round edge might not look like much, but if you use 1mm thick binding, then that 0.5mm extra dip is going to look slightly odd. Of course you can always sand the edges of the guitar slightly first to reduce the rounded distance to 1mm.

The hardest part to cut the binding rebate in is around the neck area where you've got a set neck guitar. The rest can normally be done with a suitable routing bit (though arched-top guitars an make even this awkward), but near the neck you'll need to use a sharp chisel and do it by hand. You'll may have to use two pieces of binding instead of a single piece in order to be able to feather the binding so it doesn't stand proud of the body around the neck join. Normally, the binding is fitted before the neck is attached, so that the binding follows the full depth rebate and is then cut/sanded down to produce the feathered edge.

Adding binding to the neck is hard to do, as it means full fret removal, then the binding added (again, very hard to do well on set-neck guitars where the board is over the body), then a refret and levelling and profiling the frets. Of course you can remove the neck to do this (providing that the manufacturer used a glue that can be steamed apart) , but it's a lot of work (and hence cost if not doing it yourself).

I know what yo mean. I've got at leat one satin-finished Gibson that I mean to spray with a gloss clearcoat. It'll take a few coats to build up enough depth to fill the grain (this is normally done with a sanding sealer after any staining but before any clearcoat - but for the satin finishes on the cheaper models this is normally left off to save time and money). but then a few more coats and you can rub the clear down and polish it up.

With a 'TV yellow' finish MM, you really just need to finish the process for a proper TV yellow. The mahogany bodies weren't grain filled until after the base colour coat was applied, and then a mahogany coloured grain filler was used on top, to highlight the grain in the body. This was scraped then sanded back to just leave the grain filler in the pores, over which the clear coats were applied. So you could do something very similar to a yellow MM, though I'd probably spray one coat of light amber tinted lacquer on first to tone down the yellow slightly, before the clear lacquer coats.

Of course for TV yellow, the original base coat was white, and a clear coat applied on top. So they would originally have looked white, apart from the fact that in the '50s, the nitro clearcoat wasn't fully clear and had a slight amber tint to it. Neither the white nor the clear coat were colour-fast, and faded in UV light to become more yellow. After a while, a non-tinted clear nitro lacquer was developed, which meant that the base coat now became a more creamy-yellow as the guitars now looked too white if the 'clear' clear coat was used.

Incidentally there was no such official finish as 'TV yellow'. I think the original finish was just called white. The 'TV yellow' moniker was applied later to the LP Jrs that Les Paul and Mary Ford used on their TV show, but only once they had discoloured a bit more and now did look properly yellow. As they never used LP specials, no original twin P90 special can really be called 'TV yellow'. However Gibson now seem to have made it an official colour, though this can vary from the correct base coat/grain filler/clearcoat finish to a simple satin plain yellow. Let's hope this last travesty gets sorted out by Gibson under their new management (though I doubt it).

And obviously the 2003-2006 MM isn't really a MM at all as it has the dog-ear P-90, so is much more like a LP Jr with a narrow headstock. Except it's missing the wrap-over bridge and has the T-O-M bridge and stop tailpiece.

I don't mind these Gibson mash-up guitars, but I do wish they'd given them unique names and not watered down original model types. I have a 2014 Les Paul Melody Maker, which is nothing at all like a Melody Maker but a skinny LP with two P90Ss and a 'faded' satin finish. It has a lightly arched maple-capped mahogany body and a standard LP headstock - so nothing like a MM or even a Jr (apart from the wrap-over bridge). Nice guitar, stupid name!